Exposure of humans to high levels of woodsmoke is associated with adverse health effects including asthma, respiratory disease and cardiovascular disease. In the US alone, more than 100,000 people annually are exposed to elevated woodsmoke levels from wildfires, prescribed burns and agricultural field burning. 70,000-80,000 people involved in wild land fire fighting also receive substantial occupational exposure to woodsmoke. Investigating the relationship between woodsmoke exposure and adverse health effects is hindered by inadequate methods of exposure assessment, which lead to exposure misclassification, and the setting of community-impact-driven guidelines for managed fires suffers from a lack of exposure-response data. The primary objective of this proposal is to develop biological markers of human exposure to woodsmoke. Preliminary work has shown that levels of a number of substituted methoxylated phenolic compounds are increased in urine following woodsmoke exposure. It is our hypothesis that the dose-dependent increase in urinary methoxyphenols observed following ingestion or inhalation of woodsmoke combustion products can be related in a quantitative manner to environmental woodsmoke, and thereby provide a biomarker basis for assessment of woodsmoke exposure in occupationally and environmentally exposed populations. To test this hypothesis, we plan to conduct human exposures to woodsmoke from an open fire. Exposures will be characterized using time-integrated personal sampling and area monitors. The following parameters will be measured: particle mass, particle-associated methoxyphenols and vapor-phase methoxyphenols. In addition, time resolved exposures will be assessed using data logging nephelometers at fixed locations and personal nephelometers. Urinary methoxyphenols will be determined before and after woodsmoke exposure, by using gas chromatography/mass spectrometry. In addition, we plan to measure methoxyphenol levels in urine samples collected from wildfire fighters who have elevated occupational exposure to woodsmoke. A validated biomarker of woodsmoke exposure will facilitate exposure assessment for studies investigating adverse effects of woodsmoke exposure in humans, and could be used to evaluate the effectiveness of interventions to reduce woodsmoke exposure in domestic and occupational settings. This proposed study addresses NORA research priorities related to asthma and COPD, exposure assessment methods and control technology/personal protective equipment.